VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 Chevrolet Hydraulic shocks and leaf springs

Are there any specific tests to see if the original hydraulic shocks and leaf springs on my 40 Master Deluxe Sport Sedan are ok. It has knee action suspension. It really oscillates a long time when you push down and let go. I haven't done any work or even checked to see if there is fluid in the hydraulic shocks yet. Any help/advice will be greatly appreciated.

It really oscillates a long time . makes me think it is in need of repair . frank

Good shocks are very stiff and won't bounce or oscillate. You will feel that they are very hard/impossible to push down and they will not remound. If you manage to get them down by putting a lot of weight on them they just come back up, no bouncing. It is common for bad shocks to leak which means if they had hydraulic fluid in them lately you will see the affects of the leakage around the shock location. Everything will look discolored by oil grim in the area, like oil has been spilled over a muddy surface, you may actually see oil dripping onto your floor in the area of the shocks. Another simple test is to run your finger under the shafts/arms of the shock near the shock body. If your finger picks up any sign of fluid or moist grim they are leaking. Bad shocks with slow leaks can be continually refilled to restore their stiffness but it does not last long and you will get tired of taking the wheels off all the time and the mess on the floor. I would never drive a car over 40 miles an hour with bad front shocks. The front suspension will jump and wander all over. The least little wear in a road surface could send the front end quickly right or left. You will need to keep both hands on the wheel at all times.

It is not uncommon to hear that the bushings around a shock arms have resealed themselves (don't leak) by the swelling of the material in the bushing. I tend to wonder if this is just wishful thinking, and within a few months I think the problem will reoccur. But at the cost of a shocks and the work involved in replacing them it is well worth trying.

The first thing to do is to refill the reservoir on the top of each shock with hydraulic fluid. This is not easy to do because of the location of the reservoir plug. You will need the car on jack stands and have the wheels off. Most use some type of an eye dropper or oil can with a long neck to refill their shocks. I think overfilling the reservoir is not good, so try to leave about a half to a quarter inch of space in the reservoir for expansion of the fluid when the shock hits a bump. I think, too much fluid and you may ruin a good shock. If in doubt leave the cap loose and it will seek its own level, leaking the excess out around the plug. Don't forget to retighten the plug after a few hours of driving on a variety of road surfaces. The plug doesn't need to be air tight so don't over tighten it. If you do not know how tight it is try to take it off with a socket or box wrench to keep from ruining the plug.

There is no way to repair shocks without a lot of machine shop experience and special parts and tools. Almost all begin to save their money to replace the shocks (including the two in the back). Apple Hydraulics seems to be the better choice if you need prompt service. It will cost you between $700 and $800 for four shocks, plus a core charge if you do not return the shocks with in 90 days. So don't order them until you are ready for the work.

It is easiest to replace the shocks with all the front sheet metal off the car. The inner fenders are very close to the nuts holding the shocks to the crossover member of the front suspension. Try to use only sockets on the bolts. You will need a good impact wrench or a breaker bar to loosen the nuts.

I will provide more info on actually removing the shocks later with some pictures. Good luck, Mike

P.S. Last week I replaced my front shocks. I should know how good they work in about a month!!!

I'd start with checking the oil in the shocks. It makes a huge difference especially if they are dry. The oil may or may not leak right out but you will soon know after adding the oil if that is the issue.

Good morning Mike.
Since the front end (fenders and radiator assembly)and the engine removed (pulled yesterday and sent for rebuild), I plan on checking the hydraulic shocks today. I have budgeted for replacement of all shocks and leaf springs along with the various subassemblies. You're right about having the fenders out of the way! Those are excellent suggestions about what course to take.
I'm pretty much concentrating on the front of the vehicle and not the rear (leaf springs and shocks) at this time. (Sort of working front to back.)
After I fill the hydraulic shock (not all the way up!), I'll test it out and see what happens today. It acts like a runaway rocking-horse right now.
I do have a 1940 Chevrolet Shop Manual, but I look forward to the pics you'll show me down the road. The Chevy shop manual has been reproduced so many times, the old photos loose their definition and get darker and darker with time.

I really appreciate your explanation on what to do and when to do it!

Thanks Mike.

Curt

Hi Curt,

I look forward to helping you. I am busy most of today so will get back to you probably tomorrow. Unfortunately, you will not be able to fluid check your shocks with no engine weight on them. But you can try to check for leaks by bench checking them once they are off of the car. My pictures will show what a leaking shock area looks like.

Since you have the car apart I would strongly recommend replacing the shocks. I would also not buy shocks from any ebay source. For the money/time you invest, you need to know that this is a reliable repair. I can also walk you through rebuilding your front suspension.

You should replace the rear shocks, and that is a lot easier. If the car sits level in the back I would leave the springs alone, just clean them up and make sure the grease fittings for their mounts are functioning and have good rubber bushings.
Good luck, Mike

P.S. I even have made videos on DVD of my suspension work.

Great information Mike ! I plan to follow your instructions on my 40 SDSC too, in a month or so . Great post and info. Will be following closly.....Martinomon

You're right Mike. I just found out you can't check those front shocks
with the engine out. I can barely make it bounce!
I agree with you about getting the shocks repaired
or replaced. I'll most likely send the cores in for replacement.
Since the front is void of any obstructions, I want to
rebuild the front suspension, so, since you've "been
there, done that", any tips would be appreciated.
Also, how best can I prep the front end for painting.
I've heard good reviews about the POR15 product
line. I would like to paint under the fenders, frame, floor
pans, anything prone to rust under the vehicle. I will not take the body
completely off, but will try to raise it enough to remove superficial rust
and then paint. I'll install new body to frame gaskets as well.
This body is in good condition and will need minor
repair. It's amazing how much needs to be properly done!
I've been keeping a photo journal of this restoration.
:-)
Curt

Hi Curt,

Lets answer some of your questions then start a new post heading under 40 front suspension, and I will start another post under Por15 in the Mr. GoodWrench-Technical chat area under the sub heading Body-sheet Metal, Paint and Wood so this post doesn't run on forever. All the things you have posted are right on for what you should be considering, especially documenting the work you do. I use a video camera for all most all my documentation.

One thing you should consider is doing Advance Searches of our past chat posts so you can see what discussions we have had on the various topics you will want info on as you restore your car. The best advice I can give on Searches is to try to identify only one search term and then keep changing the length of each search in 1 year durations. So search "brakes" from the period older than one week to newer than 1 year. You may even need to do a search over only 6 months on some popular topics because the search will only bring up 50 posts at a time.

So lets get the shocks safely off your car. Start by reading the manual for the steps they suggest to remove the shocks. The front springs can be very dangerous if removed without a plan to gradually relieve the pressure they are under when compressed. I use a 6 inch threaded bolt to release most of the pressure a long with my floor jack to finish the job. Work on only one side of your suspension at a time. Take the sway bar link off first, then remove the A Arm Shaft bolt closest to the center of the cross member (see picture #2) Put the 6" bolt in its place and hand tighten it all the way tight. Now remove the remaining 3 A Arm shaft bolts from the cross member. Using an open end wrench slowly untighten the nut letting the A Arm slide down towards the floor. When it has slid the 6 inches the spring has lost about 80% of its tension. Put a floor jack under the A Arm and jack it up about an inch and take the nut of the bolt and lower the A Arm to the floor on the bolt. The spring can now be easily removed or will fall out.

Next carefully follow the steps in the manual to remove the shock absorber pivot pin (see picture # 4 and #5). You will need a 1 1/16 inch socket and a good impact wrench or a 1/2 inch breaker bar. With the pivot pin off you can now remove the 3 nuts holding the shock absorber to the cross member. You're now ready to do the other side. I am sending you a personal message (PM) with my phone number. To follow up on further recommendations. Good luck, Mike


Picture #1 shows the discoloration seen in the area of a leaking shock


Picture # 2 shows the cross member where the A Arm Shaft is bolted to it. Replace left bolt with the 6" bolt...


Picture #3 shows the tool used to remove the spring tension, and the socket totake the pivot pin out. You will need a 1 1/16th" socket and it seems that a 1 1/8th" socket to do front suspension work.


Picture #4 shows the pin that has to be removed to remove the shock.


Picture #5 shows the parts that make up a pivot pin

Thanks for the VCCA search tips and the other points in the first paragraph.
I'll be studying this suspension section.
-Curt

so I am looking for some help about this suspension, I have the exact suspension on this car and I was wondering what the car is so if I have to order parts I have an idea of what I need, my car is pieced together and I am having a hard time figuring out what it actually is. any help would be great! thanks in advance

In 1940 the Special Deluxe and Master Deluxe had a coil spring front suspension. The low priced Master 85 had leaf springs, a straight axle, and tube type socks.
The factory model number would be a KB.

Great description and photos Mike

To follow up my original inquiry, I did remove all my shocks and sent all 4 to Apple Hydraulics. That is a very good company and they did fine professional work. The cost was approximately $800.00. If you follow the Chevrolet shop manual and the advice given by others that have done this before, it's not that big of a deal to remove and replace them. My car rides great with these newly rebuilt shocks. (They rebuilt my originals.)

If your shocks are doing what mine used to do, take them off and send them to Apple Hydraulics. Their turn around time was a little under 2 weeks or so. That is a major safety issue and leaking, worn out shocks should be replaced or rebuilt.

Curt

Hi Mike,

I'm wondering if you still have DVDs of your suspension work and if you would be willing to sell a few copies?

Please let me know,

Kirk

Hi Kirk,

I have not been home for several days so could not check my DVD collection to see if I had filmed the removal of my shocks. I indeed have good tape on this topic. I can send you a DVD for $15.00. Let me know if you are still interested by sending me a PM (Personal Message), or emailing me at michaeljbuller@yahoo.com.

Best wishes, Mike

Front shock replacement in progress. The large pin has me thinking I’m bot smart enough to get it together. Any special advice you could share?
Korhonj@gmail.com. Thanks

Hello JAK40.

It’s been seven years ago since I removed all of my shocks and had Apple Hydraulics rebuild them. So, it’s a bit foggy on how I proceeded.

The above posts should help, especially Mike Buller’s excellent photos and helpful posts.

If you have the 1940 Shop Manual, go to page 65. There you will see an excellent cross-section of the Upper Control Arm Assembly. Just read up and study the photos, removal procedures and you should have no troubles. I do
remember that after you remove the bolts on each side, you use an Allen wrench to remove the inside “pivot pin”. See above photo on Mike Buller’s post.

I’d be extra careful to make sure there are no hidden “loads” on the shock and to make sure front end is secured as recommended in service manual (jack
stands,etc.).


I highly recommend Apple Hydraulics for rebuilding. I sent all 4 to them.

www.applehydraulics.com

The rubber seals that go between the front bushings/control arm and center part of the pivot pin will need replacing. They keep the grease inside. Those can be purchased from Chevs of the 40’s or The Filling Station.

Good luck,
Curt

As said in my first post. GET A SHOP MANUAL. available from the Filling Station. Best $20 you can invest in an old car.

The front shocks came out without much trouble. The 3/8" nuts (3) that hold the shock in, came off except for one. The bolt head is hidden under the coil spring but I carefully cut off the nut. Now I can likely do the replacement without spring removal.
All 4 shocks are at Apple Hydraulics. Then find a shop that can do caster and chamber on such an old girl. Thanks Curt and Gene.

If the car is a leaf sprung front most car alignment shops no longer have the tools to adjust though most likely wont need much. You maybe better going to a truck alignment shop as they would have all the necessary tools. Caster is adjusted by shimming the axle at the rear "u"bolt in relation to the front "u"bolt but caster requires bending the axle so the wheel stands up right.
Tony

I’m glad you got them off okay.

I am still very pleased with Apple Hydraulics work. My car is a daily driver and the rebuilt shocks are doing just fine.

Curt